I. Field of the Invention
This invention relates to gate valves for the control of fluid flow through a pipeline and, in particular, to a dual gate valve incorporating a main gate and a follower gate for the controlled interruption of flow thereby reducing wear on the seals associated with the valve.
II. Description of the Prior Art
Gate valves for the control and interruption of fluid flow are widely utilized in the petroleum services area. Typically, these prior known gate valves incorporate a movable gate having a throughbore formed therein which can be moved into and out of alignment with the pipeline passageway using well known manipulation mechanisms. An elastomeric or metal-to-metal seal seated within the main passageway engages the gate to direct fluid flow through the gate. Due to the abrasive fluid flow through the valve, particularly when the gate is partially open, the seals can be damaged requiring replacement. The problem is exacerbated in valves used to control the flow of slurry fluids which contain a higher concentration of abrasive fluids.